1. Field of the Invention
The present invention relates to a motion adaptive frequency folding method and circuit suitable to a system having a restricted frequency band, such as a television, video tape recorder, laser disc player or the like for folding a signal component having a predetermined frequency over a signal component below the frequency.
2. Description of the Prior Art
In general, it is well-known that a conventional VHS video tape recorder is incapable of recording a signal having a high frequency above 2.5 MHz from the view point due to the limited characteristics of the magnetic video tape which contributes to a deterioration of a picture image upon reproduction by the video tape recorder because only 60% of a television signal band is utilized in the system.
Meanwhile, a super-VHS video tape recorder can send a signal beyond a television signal band so as to provide an excellent picture image, but it is not compatible with the existing VHS video tape recorder. That is, when a signal recorded by a standard VHS video tape recorder is reproduced by means of the super-VHS video tape recorder system, the resolution of the reproduced signal is deteriorated considerably. Further, the super-VHS video tape recorder requires a magnetic tape of a high standard as well as a recording/replaying apparatus of superior quality.
To address this deficiency, a video signal recording/replaying apparatus which can record a video signal having a bandwidth wider than that of a video signal to be recorded by the standard VHS video cassette recorder onto the standard magnetic tape and is compatible with the standard-VHS video cassette recorder has been proposed in, for example, U.S. Pat. No. 5,113,202.
With the patent, a motion signal indicating a movement of the video image to be reproduced is appropriately extracted and then the extracted motion signal is modified and recorded into a color signal.
The motion signal is used to control a transmission of a full band-width signal arears to be unfolded in an original frequency band during reproduction by the system, wherein a high frequency component of a brightness signal is folded over a low frequency component thereof.
According to the construction, however, when the motion signal is not correctly detected upon reproduction of a picture image, the picture image is deteriorated in quality because of artifacts such as dot crawl patterns or the likes occurred owing to frequency interleaving between the to motion signal and a folding carrier.